Numerous techniques have been developed for circulating the blood of a patient outside the body in an “extracorporeal” circuit and then returning it to the patient. For example, in dialysis for patients with kidney failure, blood is circulated extracorporeally and contacted with a large membrane surface separating the blood from a dialysate solution, and urea and other blood chemicals are migrated across the membrane to cleanse the blood, which is then returned to the patient. Another example of extracorporeal circulation is cardiopulmonary bypass (“CPB”), the procedure of mechanically bypassing both the heart and lungs to allow the whole heart to be isolated for surgical repair.
Several complications may arise in circulating blood outside of the patient's body. For example, contact of the blood with the foreign surfaces of the extracorporeal circuit triggers a massive defense reaction in blood proteins and cells that has been called “the whole body inflammatory response.” U.S. Pat. No. 5,957,880, herein incorporated by reference in its entirety, describes an improvement in extracorporeal circulation that employs contacting nitric oxide gas with the circulating blood. The nitric oxide gas was found to inhibit activation of blood platelets, thereby effecting a reduction or prevention of the whole body inflammation response heretofore associated with use of such apparatus.
In the 1980's, it was discovered by researchers that the endothelium tissue of the human body produced nitric oxide (NO), and that NO is an endogenous vasodilator, namely, an agent that widens the internal diameter of blood vessels. Since this discovery, numerous medical applications of NO have developed. Researchers have discovered that inhaled NO may be used to treat various pulmonary diseases in patients. For example, NO has been investigated for the treatment of patients with increased airway resistance as a result of emphysema, chronic bronchitis, asthma, adult respiratory distress syndrome (ARDS), and chronic obstructive pulmonary disease (COPD).
NO has also been investigated for its use as a sterilizing agent. It has been discovered that NO will interfere with or kill the growth of bacteria grown in vitro. PCT International Application No. PCT/CA99/01123 published Jun. 2, 2000 discloses a method and apparatus for the treatment of respiratory infections by NO inhalation. NO has been found to have either an inhibitory and/or a cidal effect on pathogenic cells. Delivery of the nitric oxide in the gaseous phase is preferably through a device having a specially designed nasal-cannula or a mask having a modified Fruman valve. Nitric oxide containing gas has been administered topically to treat infected tissue on the skin surface. In U.S. Pat. No. 6,432,077, Stenzler teaches that topical application of nitric oxide to wounds and/or skin of mammals is beneficial to wound healing because the nitric oxide decreases further infection. In U.S. Pat. No. 6,793,644, Stenzler describes a method of bathing the infected tissue with nitric oxide containing gas, while providing for effective evacuation of the nitric oxide containing gas from the area surrounding the infected tissue.
NO has been investigated as an agent against pathogens and microorganisms, such as viruses, bacteria, mycobateria, parasites, and fungi. Nitric oxide has found utility as a bactericidal agent. Additionally, several researchers have documented the antiviral effects of NO. Cells infected with influenza virus A/Netherlands/18/94 were treated with NO, an experiment described in Rimmelzwaan, et. al., “Inhibition of Influenza Virus Replication by Nitric Oxide,” J. Virol. 1999; 73:8880-83, herein incorporated by reference in its entirety. Results show the effectiveness of NO as a preventive therapy to viral agents. Additionally, a study by Sanders, et. al. demonstrates the effectiveness of NO as an antiviral agent, particularly against human rhinovirus. See Sanders, et. al., “Role of Nasal Nitric Oxide in the Resolution of Experimental Rhinovirus Infection,” J. Allergy Clin, Immunol. 2004 April; 113(4):697-702, herein incorporated by reference in its entirety.
U.S. patent application Ser. No. 10/658,655 describes a method for systematic delivery of the nitric oxide moiety in an extracorporeal circuit to reduce whole body contamination by pathogenic or toxic substances. Specific applications of the Ser. No. 10/658,655 application focus on managing bacteremia (blood poisoning) and/or septicemia in mammals. The Ser. No. 10/658,655 application describes the method of reducing pathogens in the mammal's blood stream to include the steps of: (1) providing an extracorporeal blood circuit; (2) circulating the mammal's blood through the extracorporeal blood circuit; and (3) exposing the blood in the circuit with nitric oxide gas in a concentration sufficient to reduce pathogenic content in the blood.
Accordingly, there is a need for a device and method for the extracorporeal treatment of the blood by the administration of nitric oxide containing gas. The exposure to NO containing gas could be used in combination with other extracorporeal procedures such as dialysis to provide for a defense against infections or as a stand alone method for decontamination and/or treatment of the blood. The treatment serves to effectively contact the blood with the nitric oxide containing gas so as to reduce the concentration of pathogens in the blood. The methods consider how to best contact the pathogens in the blood. The methods consider how to remove dissolved nitric oxide gas from the treated blood so that the blood returned to the patient has a safe concentration of dissolved nitric oxide gas therein.